1. Technical Field
The present invention relates to a liquid droplet discharge device.
2. Related Art
Heretofore, known is an ink supply system for supplying ink to a discharge head capable of discharging the ink through an ink supply pipe from an ink tank storing ink. In the case where such an ink supply system is employed, when the ink is not supplied for a long period of time after the ink is supplied to the discharge head, the ingredients contained in the ink remaining in a flow path of the ink supply pipe precipitate in some cases. When the ingredients contained in ink precipitate, ink cannot be stably supplied to the discharge head or poor discharge occurs in some cases when supplying ink to the discharge head again.
Particularly when inorganic pigments (e.g., titanium oxide), metal pigments (e.g., aluminum), and the like are contained as the ingredients of ink, there arises a problem in that these pigments are likely to precipitate due to a difference in a specific gravity from a solvent.
For example, JP-A-2006-272648 discloses an ink supply system in which a subtank for always holding a fixed amount of ink in an ink flow path. JP-A-2006-272648 also discloses providing a stirring ball in the subtank in order to stir ink in the subtank, for example. By providing such a subtank, the precipitation of the ingredients, such as pigments, contained in ink, can be reduced.
However, in the above-described former technique, when the ink supply is started after the ink supply system has stopped for a long period of time, supernatant liquid having a low pigment concentration in the ink flow path is supplied into the subtank, which has resulted in the fact that the concentration of the pigments contained in the liquid has not been sufficiently recovered in the subtank in some cases. Therefore, liquid having a low pigment concentration has been supplied to the head, which has sometimes resulted in a failure of discharging favorable liquid from the head.